A 2-year-old girl presented with recurrent abdominal pain. She was admitted in pediatrics for detailed work up. When her blood was drawn for investigation it was milky white. Yellowish white papules noted on the dorsum of hands. On fundoscopic examination opalescent retinal vessels were seen. Fasting triglycerides >1000mg/dL, but cholesterol level was normal. What is the diagnosis?

**Core Concept**
The question is testing the ability to diagnose a rare genetic disorder characterized by abnormal lipid metabolism, leading to elevated triglyceride levels and characteristic clinical features.

**Why the Correct Answer is Right**
The patient's symptoms and laboratory findings are classic for Abetalipoproteinemia, a rare autosomal recessive disorder caused by mutations in the MTTP gene. This gene encodes the microsomal triglyceride transfer protein (MTTP), essential for the assembly and secretion of very-low-density lipoprotein (VLDL) particles. As a result, the patient's liver fails to secrete VLDL, leading to severely elevated triglyceride levels (>1000mg/dL). The opalescent retinal vessels are due to accumulation of lipids in the retinal pigment epithelium. The yellowish white papules on the dorsum of hands are a characteristic skin manifestation.

**Why Each Wrong Option is Incorrect**
**Option A:** This option might be tempting, but it is incorrect because the patient's symptoms and laboratory findings are not typical of Familial Hypercholesterolemia (FH), which is characterized by elevated LDL cholesterol levels, not triglycerides.

**Option B:** This option is incorrect because Acute Pancreatitis is a complication of hypertriglyceridemia, but it is not the primary diagnosis in this case.

**Option C:** This option is incorrect because Hypothyroidism can cause elevated triglyceride levels, but it would not explain the characteristic clinical features, such as opalescent retinal vessels and yellowish white papules on the hands.

**Clinical Pearl / High-Yield Fact**
Abetalipoproteinemia is a rare genetic disorder that requires prompt diagnosis and management to prevent complications such as pancreatitis, hepatosplenomegaly, and retinal degeneration.

**Correct Answer:** D. Abetalipoproteinemia.

✓ Correct Answer: A. Familial chylomicronemia syndrome